Does it makes sense to carry a round that is just slightly slower than the speed of sound to prevent hearing damage? The rounds listed below are just less than the speed of sound but have some decent oomph.
No it doesn't make much sense. The old addage stands and it doesn't mention noise. Choose the most powerful round that you can, with a bullet suited to the task, from a gun that you can shoot well. Fortunately there are a number of good choices and some make less noise than others. Choose wisely.